1) Field of the Invention
The present invention relates to a projector.
2) Description of the Related Art
A dot-matrix display device is widely used as an image display device, such as a liquid crystal panel (a liquid crystal display device), a cathode ray tube (CRT) display device, and a plasma display device. The dot-matrix display device displays an image by a number of pixels that are arranged periodically in a two dimensional array. However, the periodic arrangement of the pixels causes a sampling noise that deteriorates quality of the image, which makes the image rough and less smooth. One of the methods to reduce deterioration of the quality of the image is disclosed in, for example, Japanese Patent Application Laid-Open No. H8-122709.
The dot-matrix image display device has a light-shielding portion called a black matrix. The black matrix is an area between each of the pixels to suppress an unnecessary light. In recent years, it is getting more popular to watch a large screen from comparatively close distance. For this reason, a watcher may recognize a black matrix image in a conventional dot-matrix image display device, resulting in the deterioration of the quality of the image. The conventional technology disclosed in the Patent Publication 1 can hardly reduce the deterioration of the quality of the image caused by the black matrix image.
One of the ideas to prevent the black matrix image from appearing is to input a light from the image display device into a prism group. Flat surfaces of the prism group transmit the light as it is; while refracting surfaces refracts the light. The light transmitted the prism group includes a straight light from the flat surfaces and a refracted light from the refracting surfaces. The refracted light is deflected and forms a pixel image on the black matrix area. As a result, the black matrix image becomes hard to recognize.
However, the projector is generally used to project a picture image, such as a film, and the text images, such as a character, a graph, and a chart, in the presentation. If the projector projects the text image using the prism group, the text image gets blurred and the quality of the text image lessens. Moreover, having two projectors for each purpose, projecting the picture image and projecting the text image, is wasteful. Consequently, having one projector that projects the high-quality image in the various uses is preferable.
The present invention is made to solve the above problems and the purpose of the present invention is to provide a projector that projects a high-quality image in the various uses, such as projecting a film, the presentation.